Effects of suppressor of cytokine signaling 1 gene promoter demethylation on cell proliferation and apoptosis in myeloid leukemia cells

  Objective  To investigate the effects of demethylation of the promoter of suppressor of cytokine signaling 1 (SOCS-1) in myeloid leukemia (ML) cells on cell proliferation and apoptosis.

  Methods  The bone marrow specimens of 78 ML patients (experimental group) and the human ML cell lines U937, HL-60 and K562 were collected as research objects, and bone marrow specimens from 50 healthy donors were collected as control group. Methylation-specific polymerase chain reaction (MS-PCR) was used to detect the methylation status of SOCS-1 gene promoter in bone marrow specimens of ML patients, quantitative real-time polymerase chain reaction (qRT-PCR)was used to detect the expression of SOCS-1 mRNA in bone marrow specimens of ML patients and human ML cell lines; Western blot was used to detect the expression of SOCS-1 protein in bone marrow specimens of ML patients and human ML cell lines. U937 cells were treated with 0, 0.8, 1.6 and 3.2 μmol/L Decitabine (DCA), and were selected as blank group, DCA-L group (DCA low-dose), DCA-M group (DCA medium-dose) and DCA-H group (DCA high-dose). MS-PCR was used to detect the SOCS-1 gene promoter methylation status in each group of cells; qRT-PCR was used to detect the SOCS-1 mRNA expression in cells of each group; western blot was used to detect the SOCS-1 protein expression in each group of cells; CCK-8 method was used to detect the cell proliferation in each group; flow cytometry was used to detect the cell apoptosis in each group.

  Results  SOCS-1 was hypermethylated in ML patients, and the expressions of SOCS-1 mRNA and SOCS-1 protein in ML patients were significantly lower than that in the control group (P < 0.05); the expressions of SOCS-1 mRNA and SOCS-1 protein in human ML cell lines U937, HL-60, and K562 was significantly lower than that in human bone marrow stromal cells HS-5 (P < 0.05), and the expression levels of SOCS-1 mRNA and SOCS-1 protein in U937 cells were the lowest, therefore, the U937 cells were used as the research objects for follow-up experiments. Compared with the blank group, the SOCS-1 methylation levels and optical density 450 value (OD_{450 nm}) at 24, 48 and 72 h in the DCA-L group, the DCA-M group and the DCA-H group were significantly reduced, and the SOCS-1 mRNA and SOCS-1 protein expression levels as well as the apoptotic rate were significantly increased (P < 0.05), and the corresponding trend of the above indicators became more obvious with the increase of DCA concentration.

  Conclusion  SOCS-1 demethylation can inhibit the proliferation of ML cells and promote cell apoptosis.